activity 12 migrating mangroves and marshes · and birds. some species of animals live only in one...

A C T I V I T Y 1 2

Migrating Mangroves and MarshesEstuary PrincipleOngoing research and monitoring is needed to increase our understanding of estuaries and to improve our ability to protect and sustain them.

Research QuestionWhat do research and long-term monitoring reveal about changes in estuary habitats and the animals adapted to live in those habitats?

IntroductionAnimals and plants are adapted to survive in a narrow range of habitats. Changes in those habitats affect the animals and plants that live in them.

At Harbor Island, Texas, which is part of the Mission-Aransas National EstuarineResearch Reserve (MA NERR), there are mangroves and salt marshes. Both of these habitats occur along the Gulf Coast where the salty, tidal waters flood the salt marshes and mangroves each day. Even though these habitats occur in similar locations, different animals live in them.

Scientists at MA NERR and their colleagues elsewhere have been studying the expansion and contraction of mangrove habitat for many years. They have been trying to determine what causes areas of mangrove habitat to increase (expand) or shrink (contract). In this activity, students will learn about the species that live in salt marsh and mangrove habitats, and will look at data from long-term monitoring in order to understand how these habitats can change over time.

Climate ExtensionUsing historical data and maps from the Mission-Aransas National Estuarine Research Reserve, students will consider climate change potential impact on mangrove habitats.

Table of ContentsTeacher Guide.......................................................................................................2

Exercise 1: What Lives in Mangrove and Salt Marsh Habitats?............................4

Exercise 2: Mapping Mangroves.........................................................................16

This curriculum was developed andproduced for:

The National Oceanic and Atmospheric Administration (NOAA)and The National Estuarine Research Reserve System (NERRS)

1305 East West Highway NORM/5, 10th Floor Silver Spring, MD 20910

www.estuaries.noaa.gov

Financial support for the Estuaries 101 Middle School Curriculum was provided by the National Oceanic and Atmospheric Administration via grant NA06NOS4690196, administered through the Alabama Department of Conservation and Natural Resources, State Lands Division, Coastal Section and Weeks Bay National Estuarine Research Reserve. Support was also provided by the Baldwin County Board of Education.

Permission is hereby granted for the reproduction, without alteration, of the activities contained in the Estuaries 101 Curriculum on the condition that proper attribution is given to the National Oceanic and Atmospheric Administration and theNational Estuarine Research Reserve System (NERRS) as the source, and cite the following URL: http://www.estuaries.noaa.gov.

http://www.estuaries.noaa.gov/

T E A C H E R G U I D E

Migrating Mangroves and MarshesResearch QuestionWhat do research and long-term monitoring reveal about changes in estuary habitats and the animals adapted to live in those habitats?

Content ObjectivesStudents will understand that:

• Animals and plants have adaptations that allow them to live and thrive in different estuary habitats, such as salt marshes or mangrove habitats.

• Living things are affected by changes in their habitat.

• Habitats can expand or contract due to outside changes in things that affect either the physical components of the habitat or the organisms that help define the habitat.

• Research on habitats and species ranges, coupled with long-term monitoring, can give clues to why estuary habitats change over time.

Exercises

Exercise 1: What Lives in Mangrove and Salt Marsh Habitats?In this exercise, students research animals that live in mangroves and salt marshes. Each student completes an Animal Flash Card about one animal. Students are asked to think about how the animals are adapted to live in these two estuary habitats.

Exercise 2: Mapping MangrovesStudents study changes in the mangrove habitat at Harbor Island, located in the Mission-Aransas National Estuarine Research Reserve, between the years of 1930 and 2004. Using historical habitat maps and long term data sets, students will make correlations between air temperature and habitat composition.

Climate Extension

Using long term data sets and the correlated response of mangroves, students will predict how climate change is likely to affect the spread of mangroves and other organisms in the area in the future. Students will consider the valueof long-term monitoring in understanding the impacts of climate change.

Activity 12: Migrating Mangroves and Marshes2

Assessment Questions Assessment questions based on content covered in Migrating Mangroves and Marshes can be downloaded on the web page for this activity in the Middle School Curriculum section of the Estuary Education website at estuaries.noaa.gov.

VocabularyAdaptation – unique feature or behavior that helps an animal or plant survive in its environment.

Habitat – the specific environment where an animal or plant is able to survive.

Mangrove – any of several tree species that grow in non-freezing estuaries. There are about 12 species though the black, red, and white are most common. The word mangrove can also refer to the entire habitat created by the trees, whichis sometimes called a mangrove forest or mangrove swamp.

Marsh – a wetland habitat dominated by grasses or grass-like plants. A salt marsh is a marsh that is flooded by salty water, such as water from the ocean.

Monitoring – sampling of environment (air, water, soil, vegetation, animals) that is compared with baseline samples to see if any changes have occurred.

Range – the geographic region in which a plant or animal typically lives or grows.

Research – systematic investigation to establish facts.

Salinity – the amount of dissolved salt content in a body of water.

Wetland – an area of land that is saturated with water during at least part of the year and which supports plant life.


E X E R C I S E 1

What Lives in Mangrove and Salt Marsh Habitats?Estuary ConceptAdaptation is a unique feature or behavior that helps an animal or plant survive inits environment.

Focus Questions• What animals live in the salt marsh?

• What animals live in the mangrove habitat?

• How are animals adapted to survive in these two estuary habitats?

Performance TasksStudents will:

• Name at least two animals that live in the salt marsh and mangrove habitat.

• Explain how a specific chosen salt marsh or mangrove animal is adapted to survive in that estuary habitat.

Teacher BackgroundSalt water estuaries are areas where freshwater rivers meet and mix with ocean waters. The mixture of salt water and freshwater creates a lively, ever-changing, sometimes stressful habitat for plants and animals. As it does in the ocean, the tide rises and falls within the estuary. This creates a zone along the shoreline that is sometimes underwater (at high tide) and sometimes exposed to the air (at low tide). This “intertidal zone” has unique and important habitats, including familiar rocky intertidal (tide pool) areas where sea stars, anemones, and crabs thrive, as well as salt marsh and mangrove habitats. The plants and animals that live in these habitats must be adapted to survive in both water and air.

Salt marshes throughout the United States are typically covered with tall grasses or rushes, such as cordgrass, needlerush, or bulrush and some smaller plants, such as saltgrass and pickleweed. In the salt marshes at the Mission-Aransas National Estuarine Research Reserve (MA NERR) in Texas, cordgrasses and salt grass are common. The cordgrasses grow close together and can be about three feet tall, while the saltgrass forms dense mats and is much shorter. There are lots of places for small animals, such as crabs, to hide between the stems of the cordgrasses and salt grass. Other animals, such as snails, wander up and down thestems, or dig into the mud below the plants.

Other coastal areas along the warmer parts of the Gulf Coast and east coast of Florida are dominated by mangrove trees. At Harbor Island in the MA NERR, there are black mangroves. Mangroves have many branches that weave together. It is very hard for a person to walk through mangroves. If you tried, you would sink deep into the mud and get tangled in the branches. But that dense, tangled swamp provides a great habitat for many animals.

Both the salt marsh and mangrove habitats provide homes for crabs, snails, fish, and birds. Some species of animals live only in one habitat or the other. Other animals frequent both habitats. In general, these animals have specific


OverviewIn this exercise, students study animals that live in salt marshesand mangrove habitat along theGulf Coast of the United States,specifically at the Mission-Aransas National Estuarine Research Reserve (MA NERR) in Texas. Students create flash cards for the animals and are asked to examine how these animals have adaptations that help them live and thrive in a particular estuary habitat.

Time Required One 45-minute class period

You'll find multimedia and other resources on the web page for this activity in the Middle SchoolCurriculum section of the Estuary Education website: http://estuaries.noaa.gov.

http://estuaries.noaa.gov/

adaptations (“survival structures”) that help them survive in the salt marsh and/orthe mangrove habitat.

Teacher PreparationRead the Teacher Background above and the Student Master: What Lives in Mangrove and Salt Marsh Habitats? Familiarize yourself with the animals featured on the animal flash cards, as well as the flash card template your students will be using.

You will want to provide your students with access to materials (e.g., books, web sites) they can use to research their animals. The materials you provide do not need to be specific to coastal Texas or the Mission-Aransas NERR.

Make copies of Student Master: What Lives in Mangrove and Salt Marsh Habitats? and Student Master: Animal Flash Card. This Exercise can be used in conjunction with Exercise 2 and its' Climate Extension to connect concepts of animal adaptations to changes in habitat and climate.

Procedure1. Distribute copies of the Student Master: What Lives in Mangrove and Salt

Marsh Habitats? Have your students read the introduction to salt marshes and mangrove habitats. Ask them to imagine what it would be like to live in each habitat.

2. Now distribute copies of Student Master: Animal Flash Card. Ask your students to read over the Animal Flash Card template. Let students choose ananimal from either of the two animal lists provided on Student Master: What Lives in Mangrove and Salt Marsh Habitats? Each student will research an animal and complete an Animal Flash Card for that animal based on their research.

3. Students will need to do research on their animal using books or the Internet.

4. Decide whether or not you want students to present their Animal Flash Cards to the class. This may be a good opportunity for you to highlight the adaptations students have uncovered in their research. For example, your students might easily find these adaptations when researching the salt marsh animals:

• The snowy egrets’ best-known adaptation is their yellow feet, which theyjiggle around underwater to attract prey. Like the whooping crane, the snowy egret’s long legs and long toes help them wade through the salt marsh and walk on the mud.

• The marsh wren has excellent camouflage. Their behavior is also an adaptation that helps them avoid predators. They are very secretive and often remain hidden in dense stands of plants so it is difficult for predators to find them.

• Blue crabs have sharp powerful claws for capturing prey and protecting themselves from predators. They also have paddle-like back fins for more efficient swimming. That means that, if they can’t fight or scare off their predator, they have the option of turning and quickly swimming away.


MaterialsPer student

• Student Master: What Lives in Mangrove and Salt Marsh Habitats?

• Student Master: Animal Flash Card

5. If you want, you can collect and bind students’ completed Animal Flash Cards into a book or post them around the classroom. You could also make copies of either the student cards or the suggested answer cards provided here and distribute complete sets to your students.


T E A C H E R M A S T E R

Examples of Completed Flash CardsCommon name of animal: Gulf Marsh Fiddler Crab

Formal (Latin) name of animal: Uca longisignalis

Lives in which habitat? Salt marsh

1. What does the animal eat?

Detritus

2. Does the animal find its food in the salt marsh or in the mangrove habitat? If neither, where does the animal find its food?

Salt marsh (mud)

3. List one or more adaptations that help the animal find or eat food.

Small claw, specialized mouth parts sort biotic material from abiotic. Non-edible components are shaped into ball and discarded.

4. What are the animal’s predators?

Whooping cranes, snowy egrets, other birds, and raccoons.

5. List one or more adaptations that help the animal avoid predators.

Camouflage, retreat into burrows

6. Where does it have its young?

In salt marsh. Females carry eggs then release them into the water where they join the plankton.

7. List one or more adaptations the animal has that help it find a mate or protect its young.

Males have one larger claw that it used to attract females.

Common name of animal: Gulf killifish

Formal (Latin) name of animal: Fundulus grandis

Lives in which habitat? Salt marsh, lagoons, rivers


The killifish is omnivorous, It eats algae, vascular plants, grass shrimp, copepods, mosquito larvae and pupae, bivalve mollusks, and small fishes.

2. Does the animal find its food in the salt marsh or in the mangrove habitat? If neither, where does the animal find its food?

In salt marsh, in shallow water.


Wide range of acceptable foods.


Snowy egret, whooping crane, herons, blue crabs, larger fish


Camouflage and the ability to stay in very shallow water to avoid larger aquatic predators


In salt marsh. Female deposits eggs in shallow water in densely vegetated areas (the marsh).


Males are brilliantly colored during mating season to attract females.

Activity 12: Migrating Mangroves and Marshes 7

Common name of animal: Whooping Crane

Formal (Latin) name of animal: Grus americana



In their Texas wintering grounds, they feed on crustaceans, mollusks, fish, berries, small reptiles, and aquatic plants. When they are in the northern breeding areas in the summer, they eat frogs, mice and voles, smaller birds, fish, aquatic insects, clams, crayfish, snails, and berries.

2. Does the animal find its food in the salt marsh or in the mangrove habitat?

In wintering grounds, they feed in the salt marsh or in shallow water.


Sharp beak, quick lunge for capturing prey, long legs and unwebbed feet for wading through the water


Large mammals (like bobcats) or birds (like eagles or ravens) may prey on eggs or young.


Adults are large enough that they are rarely preyed upon. Young are camouflaged and adults defend nests and young.


Birds nest in freshwater wetlands in Canada and northern United States.


Whooping cranes have a dramatic courting ‘dance’ that involves head bobbing, wing flapping, jumping, and calling. They also have a bald patch on their heads that becomes more colorful in mating season.

Common name of animal: Snowy Egret

Formal (Latin) name of animal: Egretta thula

Lives in which habitat? Salt marsh and mangrove habitat


Small fish, crabs, shrimp, insects, amphibians, or reptiles


Snowy egrets hunt in the marsh or in the mangrove habitat, often in tidal channels or shallow water.


Quick beak for capturing prey. Snowy egrets have yellow feet which may be used to attract prey. They can be seen wiggling their feet underwater while hunting.


Nest and juvenile predators, but adults are rarely preyed upon. Humans used to shoot them for their feathers (plumage).


They nest high in trees in large colonies.


They nest in colonies in trees, sometimes quite distant from their feeding grounds.


During breeding season the adults have beautiful, flowing feathers (or plumes) that they display during courting.


Common name of animal: Marsh Periwinkle Snail

Formal (Latin) name of animal: Littorina irrorata



The marsh periwinkle snail is herbivorous. It grazes on algae, fungi, and marsh cordgrass.


In salt marsh


Food is plentiful. Snails may actually “farm”, or encourage the growth of, fungus on marsh grass stems.


Blue crabs, large fish, large birds, raccoons


They have very hard shells and can pull themselves entirely inside the shell.


In salt marsh.


Unknown

Common name of animal: Blue crab

Formal (Latin) name of animal: Callinectes sapidus



A wide variety of food, but especially mollusks including oysters and mussels


Salt marsh and more open water areas


Blue crabs have strong claws that allow them to capture and consume prey.


Fish and other blue crabs


Camouflage, strong sharp claws, aggressive behavior, paddle-like back finsfor more efficient swimming to get away fast


Blue crabs may mate in shallow water in the salt marsh or in seagrass beds,but they release their planktonic young into the coastal ocean waters.


Adult females mate only one time when they shed their exoskeletonsduringtheir last molt. Prior to this molt, they release chemicals that attract males. A male protects the female and mates with her during the molt. Spawning is timed very precisely seasonally and with the tide so that the planktonic young are carried into the coastal ocean.


Common name of animal: Marsh wren

Formal (Latin) name of animal: Cistothorus palustri



Spiders and insects, including aquatic insects


In salt marsh


Beak for catching insects


Nest predators, including mammals and birds (crows, ravens, jays)


Excellent camouflage, secretive behavior, hides easily in dense vegetation


In salt marsh


Marsh wrens may build “dummy” nests, which may act as decoys so predators are less likely to find their real nests. Some wrens also use these nests as winter shelters. Males sing to protect/announce territory during mating.

Common name of animal: Roseate Spoonbill

Formal (Latin) name of animal: Ajaja ajaja

Lives in which habitat? Mangrove habitat


Small fish, crustaceans, amphibians, reptiles, and aquatic insects


In mangrove habitat and shallow water


May feed in groups. Wide, sensitive bill is moved through water to encounter and capture prey. Long legs, unwebbed feet for wading through the water.


Nest predators include mammals (raccoons and coyotes) and birds (turkey vultures and crows).


Unknown


Nest in mangrove habitat


Nest in trees in colonies. Male and female both sit on nest.


Common name of animal: Periwinkle snail

Formal (Latin) name of animal: Littoraria angulifer



The snail is herbivorous.


In mangrove habitat


Food is plentiful.


Large fish, birds, mammals


They have very hard shells and are able to pull themselves entirely inside.


In salt marsh


Unknown

Common name of animal: Mangrove tree crab

Formal (Latin) name of animal: Aratus pisonii



Mangrove tree crabs mostly eat plant material, including mangrove leaves, but will also consume animals or parts of animals that they encounter (i.e. crab legs, fish scales, etc.).


In the mangrove habitat


Unknown


Adults are preyed upon by birds, mammals, and larger crabs.


Camoflage, actively climb and cling to branches, move rapidly, can jump from branches to mud or water.


Females carry eggs in spongy mass on abdomen and release them into the water as plankton.


Males defend territories. Adult females mate only one time, during their last molt (when they shed their exoskeletons). Reproduction occurs year-round.


Common name of animal: Mangrove rivulus fish

Formal (Latin) name of animal: Rivulus marmoratu

Lives in which habitat? Mangrove habitat, salt marsh


Insects, worms, gastropods, mollusks


Both


The mangrove rivulus fish can survive out of water for a long time, so it can flop its way from one isolated puddle to another in search of water and food.


Wood storks, other fish including other mangrove rivulus, and the Atlantic saltmarsh snake


The mangrove rivulus fish varies in color, either lighter or darker, depending on the sediment it is near.


The mangrove rivulus fish releases its eggs in the mangrove habitat where the water is less likely to dry up than isolated puddles in the salt marsh.


The mangrove rivulus fish produces both eggs and sperm, so it can fertilizeits own eggs. It does not need a mate.


S T U D E N T M A S T E R

What Lives in Mangrove and Salt Marsh Habitats?

Polar bear in native Arctichabitat

Black mangrove Salt marsh

Are you likely to find a polar bear hunting for seals in the warm coastal waters off of Hawaii? No! What if someone brought a polar bear to Hawaii – could it survive in the wild? No! Animals are adapted to survive in specific habitats. A polar bear is adapted to survive in the cold Arctic, so it has immensely warm fur. The white fur camouflages the bear, allowing it to blend in with the ice. And the bear’s powerful legs are great for running and swimming from ice floe to ice floe. Those adaptations help the polar bear survive in the Arctic. However, all that warm, white fur would probably prevent a polar bear from surviving in Hawaii.

At Harbor Island, Texas, which is part of the Mission-Aransas National Estuarine Research Reserve (MA NERR), there are mangrove and salt marsh habitats. Both of these habitats occur along the Gulf Coast where the salty, tidal waters flood the salt marsh and mangrove habitats each day. Even though these habitats occur in similar locations, different animals live in them. A marsh is a wetland habitat dominated by grasses or grass-like plants. A salt marsh is amarsh that is flooded by salty water, such as water from the ocean. Mangrove habitat is also flooded by salt water, but instead of grasses, mangrove trees dominate the landscape. Some animals are adapted to survive in the salt marsh while others live only in mangrove habitats, and some can live in both.

In this exercise, you will choose a specific salt marsh or mangrove animal to study. You need to learn which habitat that animal lives in and how the animal is adapted to survive in that habitat.

Procedure1. Read the introduction above. Then look closely at the photos of the two habitats: the mangrove and the salt marsh

habitats. Imagine what it would be like to be an animal living in each habitat.

2. Choose a salt marsh or mangrove animal to study from the lists on the next page.

3. Use references provided by your teacher to fill out an Animal Flash Card for your animal.


Selected Animals of the Mangrove

Common name Formal (Latin) name Common name Formal (Latin) name

Periwinkle snail Littoraria angulifer Mangrove tree crab Aratus pisonii

Mangrove rivulus fish Rivulus marmoratu Roseate spoonbill Ajaia ajaja

Snowy egret Egretta thula

Selected Animals of the Salt Marsh

Common name Formal (Latin) name Common name Formal (Latin) name

Fiddler crab Uca longisignalis Gulf killifish Fundulus grandis

Whooping crane Grus americana Snowy egret Egretta thula

Marsh periwinkle snail Littorina irrorata Blue crab Callinectes sapidus

Marsh wren Cistothorus palustri



Animal Flash Card

Common name of animal: ___________________________

Formal (Latin) name of animal: ___________________________

Lives in which habitat? ___________________________


2. Does the animal find its food in the salt marsh or in the mangrovehabitat?





7. List one or more adaptations the animal has that will help it find a mate or protect its young.


Draw your animal or print out a photograph and place it here.

E X E R C I S E 2

Mapping MangrovesEstuary ConceptResearch on habitats and species ranges, coupled with long-term monitoring, can give clues to why estuary habitats change over time.

Focus Questions• What causes the mangrove habitat at Harbor Island to expand or contract over

time?

• What might happen to mangrove habitat as Earth’s climate changes?

Performance TasksStudents will:

• Interpret maps showing the range of mangrove habitat in the Harbor Island area over several decades.

• Correlate severe winter weather events with mangrove habitat contraction.

• Predict likely response of mangroves to climate change.

Teacher BackgroundScientists at the Mission-Aransas National Estuarine Research Reserve (MA NERR) in Texas and their colleagues elsewhere have been studying the expansion and contraction of mangrove habitat over the course of many years. They have been trying to determine what causes mangrove ranges to increase (expand) or shrink (contract). Research has shown that the range of black mangroves is limited by winter temperatures, since mangroves cannot survive long periods of freezing temperatures. The extent of mangrove habitat expands during times when the winter weather is warmer and contracts after winters whentemperatures drop below freezing for extended periods of time. For example, in December of 1983 the temperature in the MA NERR dropped below freezing for several straight days. Individual black mangrove trees were severely damaged by this freeze and the overall area covered by mangroves contracted. Severe freeze events in December 1989 also contributed to mangrove range contraction in the 1980s. Because of their sensitivity to temperature, black mangroves may be a good indicator species for climate change. Some scientists think that, in recent years, the area of mangroves is expanding as increasing temperature allows a northern shift in the distribution of both black and red mangroves.

Climate Extension

In recent years, the area of mangroves is expanding. This expansion might beoccurring because increasing temperatures related to climate change have allowed anorthern shift in the distribution of both black and red mangroves. As mangrovehabitat expands, it may take over areas that were salt marshes. Therefore, asmangrove habitat expands in Texas, the area covered by salt marshes may contract.Long-term monitoring, like the detailed records of weather and the habitat mapspresented in this lesson, as well as precise measures of sea level, are needed to understand the complex relationships between mangrove and salt marsh habitat, the animals and plants that live in them, weather, sea level rise, and climate.


OverviewIn this exercise, students will use four maps that show the extent of mangrove habitat on an island in Texas over a 70-year period. Additional information about the severity of winter weather in the area will be used to study a real estuarine research question: “What is the relationship between mangrove range expansion and contraction and winter air temperatures?”

Students will be studying and interpreting maps and research from the MA NERR in Texas in this exercise. Exercise 2 builds on Exercise 1: What Lives in Mangrove and Salt Marsh Habitats? Exercises 1 and 2 can be used independently.

Time RequiredOne 45-minute class period

For resources and links related to this Climate Extension, look for the Climate tab on the web page for this activity in the Middle School Curriculum section of the Estuary Education website: http://estuaries.noaa.gov.

http://estuaries.noaa.gov/

One of the reasons National Estuarine Research Reserves have been established is to ensure there are protected estuaries around the United States set aside for long-term monitoring and research. Monitoring is the continuous scientific studyof an environmental variable with the goal of detecting changes over time. Long-term monitoring programs are critical for understanding climate change since climate is the average of weather conditions over long periods of time. Monitoring can provide important information on changes that occur slowly and ecological processes that vary from year to year that can only be understood with a long-term set of data. Long-term monitoring allows scientists to provide context for short-term studies. In this activity, students learn how warming temperatures cause changes in the extent and types habitat in Texas estuaries.

Teacher PreparationRead the introduction of the Student Master: Mapping Mangroves. Then read the Teacher Background above.

The number and kinds of copies you make will depend on how you want the students to do this activity: individually; as pairs; in groups; or as a whole classroom. Projecting power point slides of the maps (provided on estuaries.noaa.gov) and flipping between the slides allows students to easily compare the maps. If you project the power point slides, then each student, pair, or group will only need paper copies of the student questions and winter severity bar chart.

Alternatively if working in pairs or small groups, you can make copies of the four Harbor Island maps onto paper (or transparencies so that students can placedone on top of the other to measure change over time). And then just provide photocopies of the of the student questions, blank map of Harbor Island, and winter severity bar chart.

You may also choose to do the exercise as a whole-class activity. Project the four maps of mangrove habitat over the different years and then fill out the table together, but then providing students or student pairs only with photocopies of the winter severity bar chart and the student master questions.Procedure

1. Have students learn about black mangroves and mangrove habitat by reading the introduction to this activity. Students need to have knowledge about adaptations and environmental tolerances of black mangroves.

2. Students will first study the four mangrove range maps for the Harbor Island area. The maps can be used to see changes in the area covered by mangroves over time. Using this information, students will fill out the appropriate columns of the data table on the Student Master.

3. Based on the data table and the maps, students will answer the first question, in which they are asked to guess why the mangrove range expanded and contracted when it did. Remind students of the mangrove’s tolerances for salinity, temperature, and water depth.

4. Next, students will look at a bar chart showing freezing events at Harbor Island from 1950 through 2004. You may want to examine this chart with your students and make sure that they are interpreting it correctly. There are two different sets of data being displayed for each winter. The first set shows the number of consecutive days when the air temperature dipped below freezing. It is important to remember that air temperature is not constant over


MaterialsPer student or student pair

• Copy of Student Master: Mapping Mangroves (including blank map of Harbor Island, four maps of mangrove coverage in different years, and winter severity bar chart)

• Markers/colored pencils

the course of a day's 24 hours. For example, at Harbor Island during the winter it can be freezing at night and then quite warm the next day. That isn’t so bad for the mangrove. The second set of data shows the number of consecutive days when the air temperature never reached above freezing. Notevery winter in Texas has this second set of data but, where that data exists, itmeans that temperatures were below freezing, both night and day, for several days straight. It is that sort of “hard” freezing event that can harm the mangroves and cause the mangrove habitat to contract.

5. Students are then asked to read the explanation on the Student Master and answer questions. Possible responses to all of the questions are shown below.

6. Climate Extension: This optional extension can be used to bring climate change connections and to check for understanding. It can also connect the animals students studied in Exercise 1 with the habitats they depend on by asking for more specificity in student responses to question Q4. To complete the climate extension, students need a copy of the blank map of Harbor Island as well as colored pencils.

Questions and Possible AnswersDuring the time period… Did the mangrove range expand or contract?

1930 to 1979 Expand

1979 to 1995 Contract

1995 to 2004 Expand

Q1. Based on what you have learned about the black mangrove’s tolerances and examination of the maps and the Winter Severity bar chart, what doyou think could have caused the habitat to contract or expand?

Students should suggest that something happened between 1979 and 1995 to cause the mangrove habitat to contract during that period. Specifically, the students should speculate that contraction occurred due to the prolonged freezing temperatures in winters of 1983-84 (and they may also note 1989-90) that were indicated in the bar chart.

Q2. Based on the data in the Winter Severity bar chart, during what other years do you think the mangrove habitats may have contracted?

Students should see that there were also significant freezing events in the winters of 1950-1951 and 1961-1962. Students should speculate that mangroves were damaged by the freeze events in those two winters and that mangrove habitat probably contracted after those two winters.

Climate ExtensionQ3. Earth’s climate is changing. In Texas, scientists expect increasingly

warmer weather, with fewer days of freezing temperatures. Based on the patterns of change you saw in the earlier maps, use the colored pencils and the blank map of the Harbor Island area to show what you think themangrove area in Harbor Island might look like in 2030. Remember to put a color key somewhere on your map (i.e., what color did you use to show mangrove habitat?).

Students should understand that a warmer climate means fewer and fewer


hard winters for the Harbor Island area. This means that the mangroves will not experience the freeze-related damage. The mangrove range is expected tocontinue to expand in the future. Therefore, student maps should show a larger area of Harbor Island covered by mangroves in 2030 than is shown in the map for 2004.

Q4. What happens to animals that live in a habitat when that habitat expands? What happens when that habitat contracts or disappears?

If a habitat such as the mangrove expands, there is more area in which animals adapted to that habitat can live. Usually, they will increase their population to take advantage of the new habitat area. However, if the habitat contracts, the populations of animals adapted to that habitat will decrease. Animals may leave the area to find other locations with that habitat. If that isn’t possible, the animals will likely face increased competition in the remaining habitat’s area and their populations may decrease.

Q5. In the study of climate change impacts, why is it important to conduct collect data over many years through long-term research and monitoringprojects?

Students could have a variety of answers that include some of the following points. Climate change is the shift in the average of weather conditions over long periods of time, but the change is not always consistent from year-to-year. Therefore researchers need to see the long-term trend or trajectory over many years instead of short-term variability. Therefore researchers inherentlyneed to develop long term monitoring projects to collect data on environmental changes that may be occurring slowly. The size of the mangrove habitat on Harbor Island varied dramatically over the 70 years, if the research project was shorter it would have only captured a snapshot of themangrove habitat, instead of the dramatic increases and decreases seen over time. In the case of the mangrove study they needed many years of data to confirm that it was temperature, not other environmental variables like salinity that were causing the impacts to the mangrove habitat.



Mapping MangrovesThe black mangroves on Harbor Island, Texas are growing at the northern limit of their range. They can’t survive any farther north because they are not adapted to the freezing temperatures that occur more frequently there. When the temperature drops below freezing, individual black mangrove trees may be damaged or killed. The longer the temperature remains below freezing, the more damage there is to the trees.

The black mangrove’s range is also limited by water salinity and water depth. The mangroves grow in brackish or salty water, not in fresh water. They also cannot grow in water that is too deep because they need to get air to their roots. Temperature, salinity, and water depth all determine where the black mangroves can and cannot grow.

On Harbor Island, the percent of the land covered by mangroves changes over time. Sometimes, over a period of one to many years, the mangrove habitat expands. Other times, mangrove trees die and the area of the island covered by mangroves contracts.

In this exercise, you will look at maps showing areas of Harbor Island covered by mangroves at four times (1930, 1979, 1995, and 2004). You will then examine information about weather events in the Harbor Islandarea that resulted in unusually cold (freezing) temperatures. From these data, you can answer the research question: “Is mangrove expansion and contraction correlated to changes in air temperature?” You will also follow-up with a hypothesis about future changes in mangrove habitat coverage on the island.

Procedure1. Read the introduction to learn about the environmental conditions needed for black mangrove survival.

2. You have four maps of Harbor Island, each showing the extent of mangrove habitat in different years. First, compare the map from 1930 to the one from 1979. According to the maps, did the area covered by mangrove habitat expand or contract from 1930 to 1979? If it expanded, write “Expand” in the appropriate box in the data table. If the area contracted, write “Contract”.

3. Now compare the maps from 1979 and 1995. What happened to the area covered by mangroves from 1979 to 1995? Did it expand or contract? Write your observation in the data table.

4. Lastly, compare the maps from 1995 and 2004. Write your observation in the data table.

Data Table

During the time period… Did the mangrove range expand or contract?

1930 to 1979

1979 to 1995

1995 to 2004

5. To look for possible explanations as to why the mangrove habitat may have contracted between 1979 and 1995, scientists examined the highest and lowest air temperatures during that period. In particular, scientists are particularly interested in how many days in a row (consecutive days) the highest air temperature was below freezing. To get an idea of what they found, examine the Winter Severity bar chart.


QuestionsQ1. Based on what you have learned about the black mangrove’s tolerances and examination of the maps and the

Winter Severity bar chart, what do you think could have caused the habitat to contract or expand?

Q2. Based on the data in the Winter Severity bar chart, during what other years do you think the mangrove habitats may have contracted?

Climate ExtensionQ3. Earth’s climate is changing. In Texas, scientists expect increasingly warmer weather, with fewer days of freezing

temperatures. Based on the patterns of change you saw in the earlier maps, use the colored pencils and the blank map of the Harbor Island area to show what you think the mangrove area in Harbor Island might look like in 2030. Remember to put a color key somewhere on your map (i.e., what color did you use to show mangrove habitat?).

Q4. What happens to animals that live in a habitat when that habitat expands? What happens when that habitat contracts or disappears?

Q5. In the study of climate change impacts, why is it important to collect data over many years through long-term research and monitoring projects?



Harbor Island Mangroves, 1930 Harbor Island Mangroves, 1979



Harbor Island Mangroves, 1995 Harbor Island Mangroves, 2004



Harbor Island Mangrove, 2030 Projection



Winter Severity, 1950 to 2004, Harbor Island


activity 12 migrating mangroves and marshes · and birds. some species of animals live only in one...

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